1. Field of the Invention
The present invention relates to the microbial industry. More specifically, the present invention relates to a method for producing L-lysine by fermentation, and a microorganism used in the production method.
2. Brief Description of the Related Art
In the production of L-lysine by fermentation, strains isolated from nature or artificial mutants thereof have conventionally been used to improve the productivity. Many artificial mutant strains that produce L-lysine are known, and include S-2-aminoethylcysteine (AEC) resistant strains and those that belong to the genus Brevibacterium, Corynebacterium, Bacillus or Escherichia. Furthermore, various techniques have been disclosed for increasing the amino acid production, for example, the use of a transformant obtained by using recombinant DNA.
As for Escherichia bacteria, for example, methods for producing L-lysine by using a strain in which dihydrodipicolinate synthase (DDPS) activity is enhanced have been disclosed in Japanese Patent Application Laid-open (Kokai) No. 56-18596, U.S. Pat. No. 4,346,170 and Applied Microbiology and Biotechnology, 15, pp. 227-331 (1982). Furthermore, a method for producing L-lysine by using an Escherichia bacterium into which DDPS derived from, and native to, a Corynebacterium bacterium has been introduced is disclosed in Korean Patent Publication No. 92-8382. Furthermore, a method for producing L-lysine using a strain which has been transformed with a plasmid containing DNA that codes for dihydrodipicolinate synthase derived from, and native to, an Escherichia bacterium which has a mutation to desensitize feedback inhibition by L-lysine, DNA that codes for aspartokinase which is desensitized to feedback inhibition by L-lysine, DNA that codes for dihydrodipicolinate reductase, and DNA that codes for diaminopimelate dehydrogenase derived from, and native to, a coryneform bacterium is disclosed in International Publication No. WO95/16042.
As for Brevibacterium bacteria, International Publication No. WO95/11985 discloses that L-lysine productivity can be improved by enhancing the activity of intracellular nicotinamide adenine dinucleotide transhydrogenase. Furthermore, a method for producing L-lysine using a strain in which phosphoenolpyruvate carboxylase activity is solely enhanced and a method for producing L-lysine using a strain in which aspartate-semialdehyde dehydrogenase activity is solely enhanced are disclosed in Japanese Patent Application Laid-open No. 60-87788 and Japanese Patent Publication (Kokoku) No. 6-102028, respectively.
The industrial production of amino acids by fermentation is performed on a large scale. Therefore, even improving the yield by several percent may provide significant industrial value, and thus improving the yield, even if only a small amount, is desirable.